Not every cell response turns on a gene
- The idea
- Predict
- See it
- Why
- Check
The idea
“When a cell gets a signal, it responds by turning genes on and making new proteins.”
Gene regulation gets a lot of class time, so it's easy to assume every response switches a gene on. Many just turn on proteins already in the cell.
The short version
The mistake: When a cell gets a signal, it responds by turning genes on and making new proteins.
What's actually true: Many responses switch on proteins the cell already has, and that takes only seconds.
- A kinase can add a phosphate group to a protein the cell already has. The protein changes shape and turns on or off within seconds.
- Other signals do change gene expression, often through a transcription factor. Copying the gene and building the protein take minutes to hours.
- When the signal stops, enzymes called phosphatases remove the phosphates, and the proteins switch back.
On the exam: A response in seconds means a protein already there got switched on. Gene expression takes minutes to hours.